1. Field of the Invention
The present invention relates to a continuous molding method for a honeycomb sandwich panel having a structure wherein a plastic composite is bonded to each of both faces of a honeycomb-shaped core member.
2. Background and Problem
Honeycomb sandwich panels with a honeycomb member sandwiched inside are widely used as a construction material, etc. particularly, honeycomb sandwich panels (hereinafter referred to as "honeycomb panel(s)") using a plastic composite are characterized by having a light weight and a high strength, and are in wide use, not only as interior materials of aircraft, such as floor material, wall material, galley and lavatory module but also as sheathing materials such as control plane, door, duct and fairing.
FIG. 6 shows a conventional structure of a honeycomb panel 1. Surface materials 20a and 20b are bonded to both surfaces of a honeycomb core member 10 and, where required, a decorative material 30 is stuck on the surface(s) of both or one of the surface materials 20a and 20b to obtain a final product.
The honeycomb core member 10 is formed using, for example, paper, plastic or aluminum, but for aircraft there is used a material obtained by forming short fibers of an aromatic polyamide in the shape of paper and impregnating the paper-like fibers with a phenolic resin.
As the surface materials 20a and 20b there are used plates and aluminum, but for aircraft there are used sheet-like prepregs obtained by impregnating fabrics or short fibers such as glass, aramid or carbon fabrics or fibers with phenols or epoxy resins followed by forming in the shape of sheet. Surface materials 20a and 20b of prepreg contain a thermosetting resin and have plasticity at room temperature. Therefore, if the surface materials 20a and 20b are laminated to both surfaces of the honeycomb core member 10 followed by the application of pressure and heat, the surface materials 20a and 20b will be bonded to the honeycomb core member by thermosetting of the resin which has been impregnated into the surface materials to form a honeycomb panel 1.
Where required, a decorative material 30 is stuck on the upper surfaces of the surface materials through an adhesive film or the like to obtain a final product.
As methods adopted heretofore for forming the honeycomb panel 1 there are mentioned a vacuum bag molding method, an autoclave molding method and a heat press molding method.
The vacuum bag molding method is the simplest honeycomb panel molding method. According to this method, as shown in FIG. 7, a releasing agent such as wax or silicone is applied onto the upper surface of a mold 40, onto which are then laminated the surface material 20b, honeycomb core member 10 and surface material 20a successively in this order. In many cases, the surface materials 20a and 20b are each one sheet, but in some specification of a honeycomb panel, they each comprise a plurality of surface materials and an adhesive sheet may be sandwiched in between the surface materials.
After the lamination of the honeycomb panel materials has been completed, the upper surface is covered with a release paper 42, which in turn is covered with a bleeder cloth 43. As the bleeder cloth 43, which is used for discharging the inside air to the exterior, there is used a non-woven fabric formed from polyester. The outside of the bleeder cloth 43 is covered with a flexible film 45 having no gas permeability such as Mylar, and the gap between it and the mold 40 is sealed using a sealing tape 47 to form a bag 48.
Then, the inside, indicated at 46, of the flexible film 45 is communicated with a vacuum source (not shown) to discharge the air from the inside 46, resulting in that the whole of the flexible film 45 is compressed by atmospheric pressure and the honeycomb panel undergoes a pressure of 1 kg/cm.sup.2. At this time, the bleeder cloth 43 functions to ensure the discharge of air from the inside 46, attain uniform pressurization and absorb excess resin discharged upon thermosetting of the surface materials 20a and 20b of prepreg to prevent the formation of air pocket between prepreg layers.
The bag 48 thus formed is put an air circulation type oven and the prepreg is hardened at specified temperature and time to form a honeycomb panel.
The autoclave molding method is used in combination with the vacuum bag molding method described above. The bag 48 in a vacuum condition is put into an autoclave (a heating and pressurizing pot), in which heating and pressurization are performed for a predetermined time and thermoset bonding is attained at a pressure not lower than atmospheric pressure. Therefore, the products obtained by the autoclave molding method are high in strength and applicable also to large-sized parts.
The heat press molding method forms a honeycomb panel by heat pressing using upper and lower molds. The productivity is high although it requires molds matching product shapes.
In the above conventional methods, since the lamination of the honeycomb member and the surface materials is performed by manual operation, the productivity is low and it is impossible to effect continuous molding.
The present invention provides a continuous molding method for a long honeycomb panel.